1. Field of the Invention
The present invention relates to a vehicular brake system that electronically controls the braking force to be applied to a vehicle according to the braking operation amount.
2. Description of the Related Art
In an electronically controlled vehicular braking system, the braking force is electronically controlled. Specifically, the hydraulic pressure that is supplied to the wheel cylinders for driving the brake system, is electronically controlled according to the amount of operation applied through a brake pedal. Such a brake system is described in Japanese Patent Application Laid-Open No. 2004-243983, for example.
With regard to the vehicular brake control system described in Japanese Patent Application Laid-Open No. 2004-243983, when a driver operates a brake pedal, a master cylinder generates a hydraulic pressure corresponding to the operation amount, and part of the hydraulic fluid flows into a stroke simulator, so that the operation amount of the brake pedal corresponding to the brake-pedal depression force is regulated. Meanwhile, a brake ECU sets the desired amount of speed reduction of the vehicle according to the pedal travel detected, and then determines the distribution of the braking force to be applied to the wheels to supply a certain hydraulic pressure to the wheel cylinders.
With regard to the conventional vehicular brake control system described above, the master cylinder, which generates the hydraulic pressure corresponding to the operation amount of the brake pedal, is provided with the stroke simulator into which part of the hydraulic fluid flows and which thus regulates the operation amount of the brake pedal. In addition, a pressurizing mechanism for pressurizing the hydraulic fluid to be supplied to the four-system wheel cylinders is provided for each system with a master cylinder cutoff valve interposed between the master cylinder and the pressurizing mechanism. Accordingly, the hydraulic system is complicated, which can make the manufacturing cost high.